As woven fabrics for screen printing, mesh woven fabrics composed of natural fibers such as silk or inorganic fibers such as stainless steel have been widely used. However, in recent years, synthetic fiber meshes excellent in flexibility, durability and cost performance are widely used. Among them, monofilaments made of polyesters excellent in dimensional stability and the like are highly suitable for screen mesh cloths. Monofilaments made of polyesters are used also for graphic design printing such as label printing for compact discs, electronic board circuit printing, etc.
In recent years, electronic devices have been making remarkable progress to achieve higher performance and more contact sizes. Accordingly, to respond to the requirements for more compact electronic boards and more precise board circuits constituting electronic devices, the demand for higher-mesh and higher-modulus screen mesh cloths with fewer woven fabric defects is growing. Therefore, as polyester monofilaments satisfying these properties required by screen mesh cloths, it is especially important that the polyester monofilaments have a smaller fineness and a higher modulus and do not cause such defects as bane and weaving bars in the production of screen mesh cloths. Compared with ordinary synthetic fibers, monofilaments have a larger single fiber fineness and a higher modulus are likely to fall or be deformed when they are wound, and the screen mesh cloths are likely to have such defects as bane. Consequently it is desired to establish package techniques capable of improving these defects.
As a monofilament package good in unraveling capability/winding stability and capable of overcoming the bane defect of a screen mesh cloth otherwise caused by the tightening of the winding increasing with the lapse of time after monofilament winding, a package wound like a cheese is disclosed (JP 8-199424 A).
Further, a method for producing a polyester monofilament, in which a high-strength and a high-modulus polyester monofilament capable of being processed into a screen mesh cloth with excellent dimensional stability can be produced easily and efficiently without fiber falling, shaving of the filament and pirn barre is disclosed in JP 2004-225224. In that production method, when a monofilament is spun, stretched and wound by a direct spinning and stretching method, a spindle is disposed with its rotating axis kept perpendicular to the progress direction of the filament running out of the stretching line so that the filament can be wound around a bobbin mounted on the spindle to form a package tapered at both the end portions thereof.
However, though the package of JP 8-199424 A suffers little fiber falling and loosening and can avoid filament breakage at the time of unraveling, a high friction oil with a coefficient of dynamic friction between yarn and mirror finished surface of approx. 0.27 to approx. 0.28 μd is used for winding as a cheese. Consequently, there is a problem that in an attempt to weave a higher-mesh and higher-modulus screen mesh cloth, the filament surfaces are shaved by the reed, to cause a disadvantage that shaving fluff is contained in the woven fabric. Further, though unraveling can be made without filament breakage, the unraveling tension variation cannot be sufficiently inhibited. Consequently, there is a problem that the weaving bars caused by it cannot be avoided. In particular, if smaller-fineness and a higher-modulus filaments are used, the problem of weaving bars is more outstanding, and therefore it is difficult to obtain a high-quality/high-precision screen mesh cloth.
Moreover, JP 2004-225224 merely indicates that the monofilament package form is tapered at both the end portions of the package, and that the taper angle is 30° C. or less (claims 1 and 3). JP 2004-225224 does not describe the package quality and form for inhibiting such defects as shaving fluff, barre and weaving bars in the weaving of the screen mesh cloth described later. Further, JP 2004-225224 does not describe any of the coefficient of dynamic friction between yarn and yarn, unraveling tension variation gradient, filament length per one traversing cycle, the winding width of the innermost layer of the package and the winding diameter of the inner most layer which are important indicators of the package quality and form. The polyester monofilament package disclosed in JP 2004-225224 cannot satisfy the properties required for weaving a screen mesh cloth.
Thus, it could be helpful to provide a monofilament package that does not cause such defects as shaving fluff, bane and weaving bars when weaving a screen mesh cloth.